It wasn’t just Australia who wanted to talk. She also had requests from Nairobi to New York, where breakfast television studios were even willing to bump Donald Trump off the news agenda in favour of this well-spoken primary school head teacher from Darlington in County Durham.

The letter in question was a four-sentence missive Miss Chisholm sent out in the school bags of her 450 pupils at Skerne Park Academy on Monday evening.

The letter Katie Chisholm sent out to parents.

It was polite and to the point. In it, she noted that parents were increasingly dropping off -- and even picking up -- children while “still wearing their pyjamas and, on occasion, even slippers”. She hoped, she said, parents agreed it was important “to set our children a good example about what is appropriate and acceptable… in preparation for their own adult life.” Ending with the sign off: “Thank you for your cooperation in helping to raise our children’s aspirations.”

Since it was sent (and posted on Facebook, where it went viral) she has received “hundreds” of emails in support. Some fellow teachers have also expressed horror at slipping standards not just at the school gates but in parenting in general. Most have applauded Miss Chisholm, 36, for speaking out.

Miss Chisholm says: “In every school there are always some parents, regardless of what type of school it is, who are either anti-establishment or think they know better. I am sure every head teacher in the country can name parents who don’t agree with them when it comes to education. But these parents have been very vocal about their dislikes. That letter gave them their chance to voice an opinion.”

Skerne Park Academy primary school.

A hardcore group of parents decided to attack the messenger, turning up the following morning in full nightwear to make their point. Others took to social media to brand Miss Chisholm as 'snobbish’.

One mother, Kim Daniel, threatening to take her children out of school, said she had seen Miss Chisholm “dressed in a low-cut top, wearing high heels.... What example is she setting the kids?”

Miss Chisholm admits that she’s disabled her Facebook account: “I don’t want to see any of the negativity.”

I am chatting to her in a wine bar in London, where she is visiting with her deputy to attend a one-day course on children’s mental health.

While she stands at 6 foot tall, despite her height she is nothing like Miss Trunchbull, the terrifyingly sadistic headteacher in Matilda, that some parents have suggested she resembles. If anything, she looks far more like the kindly, sunny Miss Honey.

Kate Chisholm has been called 'an overpaid prostitute' and a 'failed fat supermodel' by parents unhappy at her attempts to improve school standards

The fact she has managed to keep her smile is a miracle.

“I’ve been called an overpaid prostitute and a failed fat supermodel. Both times this was parents saying this to me in front of their kids. If I want to have a word with the parent about a discipline issue, say, some parents have shouted at me, they’ve sworn at me, they’ve told me that I don’t know what I am talking about.”

She insists she has a thick skin and is able to laugh it off -- even when one parent said she hoped she was barren “because if you have children, they’ll be the spawn of the devil”.

“I’ve had parents take a swing at me. It was because I wouldn’t back down over school uniform."

Kate Chisholm

When Miss Chisholm took over the Skerne Hill Academy, the primary school was getting such bad results that there was talk of it closing down. While Darlington is a relatively affluent town, Skerne Park housing estate, next to the school, is not. Of the children attending the school, 43 per cent are entitled to free school meals -- nearly three times the national average of 15 per cent.

But Miss Chisholm didn’t see this as an excuse for a lack of aspiration, and has made it her mission to crack down on parents allowing their children to skip school or turn up late; she has also improved SAT scores, appointed a full-time social worker, introduced lots of after-school activities, and even replaced French with Mandarin as the second language. At its most recent inspection, Ofsted rated the school as “good”.

She is keen to stress that majority of parents are “absolutely fantastic, wonderful people”. But there are still a small number who are resistant and are happy not just to insult her, but take it further.

“I’ve had parents take a swing at me. It was because I wouldn’t back down over school uniform. It used to be they could wear anything they wanted on the bottom half, and then a blue jumper on top. When we changed it, I insisted the parents made the children wear the jumpers with logos because I wanted the children to be feel part of a community.’

“If you respect education, you want your child to come to school on purpose -- not as an afterthought.”

Kate Chisholm

Even though she ensured every child received a free uniform paid for out of the pupil premium and sponsorship there was a backlash. One parent even decided to make it physical. “A father just got so irate he took a swing at me. I had to duck. He was massive.”

Were you worried?

“I just thought: that’s new, I’ve never had that before,” she smiles. “I asked him to leave the building.”

On Thursday, a report by the Association of Teachers and Lecturers said that 43 per cent of teachers or teaching assistants had experienced violence at school over the last year. Given a list of reasons for bad behaviour, 85 per cent of those polled said that lack of boundaries at home were to blame.

Chisholm sees turning up properly dressed as the right way to set aspirations for children.

Miss Chisholm says like all schools she has violent pupils - “Some of those children who need the most love, show it in the most unloving way,” she adds wryly. But what concerns her is not the lack of respect for teachers, but for education itself. This can not be laid at the door of the child, but has to be blamed on the parents: “If you respect education, you want your child to come to school on purpose -- not as an afterthought.”

Which is why she decided to fight the pyjama battle.

It started in September when she spotted a handful of parents wearing nightwear not only to drop off their children, but also to pick them up. “Then at Christmas we have about 12 different performances of the Christmas play, in morning, afternoon and evening. And there were parents in all of these performances wearing pyjamas.”

Is it possible they were just tracksuit bottoms? “There were big red fluffy dressing gowns, slippers, tops with sleeping unicorns.”

“It’s nice to make an effort for the children – it’s their big day. When I was a child, my Mum [who was a teacher herself] would put on this posh dress and put on perfume. And I’d see them in the audience, and it would make my day.”

She insists her objections to Pyjamas are not because she is being “snooty”, it is because she thinks the children will suffer.

“I am a great believer in brain development and how children grow. Children need boundaries and they need to know what to expect in the morning. There are studies that prove a clear routine improves children’s ability to learn, and therefore their ability to retain knowledge, their ability to progress and reach their aspirations.”

That is all she wants: for the children to flourish and reach their potential. And she’s happy to take on any parent that disagrees with her. Even those with flying fists.